Such a method is known in the marketplace and is utilized in an internal combustion engine which is built into a motor vehicle. An electric fuel pump pumps fuel from a tank to an injection valve. The injection valve injects the fuel into an intake manifold of the engine. Supply lines branch from the intake manifold to the individual cylinders or corresponding combustion chambers of the engine. The combustion chambers can be connected to the supply lines via injection valves. Depending upon which injection valve is just then open, the fuel reaches one or the other combustion chamber.
A method of the above-mentioned type is known also from such internal combustion engines wherein the fuel is injected directly into the combustion chamber of the engine. The engine can here be a gasoline engine or a diesel engine. In this case, each combustion chamber has its own fuel injection device.
In the known method, the injection time of the fuel injection device is pregiven by a characteristic line. A quantity of fuel to be injected is supplied to this characteristic line and this fuel quantity, in turn, is dependent upon the operating state of the engine and on the power wanted from the engine.
Basically, it is possible that the intended fuel quantity is not delivered notwithstanding the correct duration of opening of the fuel injection device. The reason for this can, for example, be plugged injection holes in the fuel injection device. Manufacturing tolerances can also lead to the situation that the fuel quantities supplied by different fuel injection devices are different for the same opening duration. In the known method, quasi steady state changes can be noticed from a change of the fuel consumption caused by the lambda control or by a change of the load and/or power. In many cases, it would, however, be desirable to be able to determine deviations of the actually injected fuel quantity from the desired fuel quantity with a still higher resolution.